We must find the common denominator.
The list of multiples of 4: 0, 4, 8, 12, 16, 20, ...
The list of multiples of 3: 0, 3, 6, 9, 12, 15, 18, ...
The common denominator is 12.
[tex]\dfrac{3}{4}=\dfrac{3\cdot3}{4\cdot3}=\dfrac{9}{12}\\\\\dfrac{2}{3}=\dfrac{2\cdot4}{3\cdot4}=\dfrac{8}{12}[/tex]
Therefore:
[tex]\dfrac{3}{4}+\dfrac{2}{3}=\dfrac{9}{12}+\dfrac{8}{12}=\dfrac{9+8}{12}=\dfrac{17}{12}=\dfrac{12+5}{12}=1\dfrac{5}{12}[/tex]